These messages come from the SpellCheck plugin and are harmless. The SpellCheck plugin uses the `enchant` library to perform spell checking and `enchant` is trying to load its `voikko` and `aspell` backends which are not available on Windows. This is completely OK.
The SpellCheck plugin is not enabled by default, so you must have had enabled it in the past. Uninstalling Geany removes all application data but not the user configuration (this is on purpose), so even after completely re-installing Geany, your previous settings and enabled plugin configuration is preserved.
To get rid of the messages and all spell checking functionality, simply disable the SpellCheck plugin in the plugin manager.